Valve-controlled differential pump system and method of operation

ABSTRACT

Valve-controlled differential pump system for advancing and metering liquids including a differential pump, and means for controlling the pump comprising a plurality of mechanically actuable or mechanically and pneumatically actuable three-way valves operatively connected to the pump; and method of operating the same.

United States Patent 2,90 .23. 91.19521, ia 'gpsla- L-glilll li Mentschel et al. Dec. 5, 197g [54] VALVE-CONTROLLED DIFFERENTIAL 2,943,765 7/1'960 Glasgow '6; a1? ..'...;4i7/37s" PUMPSYSTEM AND METHOD OF 1 3,151,804 10/1964 La Flame ..417/375 OPERATION 1,067,613 7/1913 Lane ..417/395 2,951,745 9/1960 Sweet et al. ..417/397 [721 Invent: Memschel; 2,973,717 3/1961 Kendig ..417/395 x Henkeh 1991 1., 19 ,Erlangcn, 3,237,646 3 1966 HOUSE! et al ..251/75 x ny 3,353,559 11/1967 Phillips ..251/75 X Assigneez siemans Akfiengesenschm, Berlin 3,419,031 12/1968 Hesse et a1 ..251/75 X M3919lb91 q Primary Examiner-Robert M. Walker 22 Filed; June 5, 19 9 Attorney-Curt M. Avery Arthur E. Wilfond, Herbert [21] Appl No 830' 832 L. Lerner and Daniel J. Tick ABSTRACT Foreign Applimfioll Priority Data Valve-controlled differential pump system for advanc- June 1968 Gennany P 17 03 545 9 ing and metering liquids including a difierential 'pump, v and means for controlling the pump comprising a pluality of mechanically actuable or mechanically and 52 US. Cl ..417 395 251 75 r 51; In CL Mb 43/06 F041) 45loo/F1691 31, pneumatically actuable three-way valves oper atively [58] Field of..." h ",w,"4l7/392 6 397 connected to the pump; and method of operating the 251/75 EIFL.. References Cited 5 Claims, 10 Drawing Figures STATES PATENTS wvnwmmw 3 WORKING GAS PA'TENTEDHEB 51972 SHEEI 2 BF 5 PATENTEU DEC 5 1972 SHEEI 5 BF 5 Fig.7

WORKING GAS-- 1 "VALVE-CONTROLLED DIFFERENTIAL PUMP SYSTEM AND METHOD OF OPERATION Our invention relates to valve-controlled differential pump and more particularly to such a pump operated by gas or vapor for advancing and metering liquids,

such as liquids in fuel cell assemblies.

Piston-type lift pumps operating with vapor and without a flywheel, for example so-called simplex and duplex pumps, have been known for a long time and are often used today as boiler feed pumps. By directly coupling the vapor and pump cylinders, a simplification of the pump assembly is in fact achieved; however, due to the indirect control, the vapor consumption per operating stroke is very high. Sealing of the discharge chamber from the drive chamber can furthermore only be achieved by means of screwed or bolted-on stufling boxes, resulting in considerable increase in frictional losses.

It is accordingly an object of our invention to provide valve-controlled differential pump system having a pump driven by gas of vapor, and especially a pump having relatively low delivery or discharge output wherein the aforementioned disadvantages of the heretofore known piston-type lift pumps are avoided. It is furthermore an objectof our invention to reduce frictional losses by replacing the pistonsof'the conventional pumps either entirely or partially with diaphragms or membranes.

With the foregoing and other objects in view, we provide in accordance with our invention, valve-controlled differential pump system for advancing and metering liquids, comprising a differential pump, and means for controlling the pump including a plurality of mechanically actuable or r'nechanicallyandpneumatically actuable three-way valves operatively connected to the pump, such a valve controlledpump having the advantage primarily of being infinitely variably controllable, as opposed to step wise control, from zerotoa maximum value.

In accordance with other features of our invention, quantity regulation is efl'ected by a temperature or pressure-dependent needle valve installed in the gas or vapor supply line of the control valve. Of course, it is within the scope of our invention for the needle valve to be controlled by other phenomena than temperature or pressure.

When the valve-controlled diflerential pump system of our invention is employed for metering fluid'fuel in a fuel cell, especially at a reformer for producing hydrogen installed upstream of the fuel cell, the con-' sumer current of the load connected to the fuel cell, can for example also be employed for quantity regulation, so that as the load increases, the quantity of liquid advanced into the reformer also increases.

In accordance with further features of our invention, we provide diaphragms or bellows entirely or partially in place of the working or operating piston and the discharge piston of the conventional pumps. Thereby, the efficiency of the pump can be increased, on the one hand, and the pump can be readily installed for use with poisonous and/or chemically corrosive i gases, vapors and liquids, on the other hand. The pump control mechanism and regulating switches of our system operate completely free of any danger of explosion and are therefore especially suitable as metering assembly for a hydrogen generator, such as a reformer for exampic.

Although the invention is illustrated and described herein as valve-controlled differentialpump systemand method of operation, it is nevertheless not intended to be limitedto the details shown, since various modifications may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The invention, however,together with additional objects and advantages thereof be best understood from the following descriptionwhen read in connection with the accompanying drawings, in which:

FIGS. 1 and 2 are schematic views of the valve-controlled difierential pump system of our invention, respectively having a simplex and a duplex pump;

FIG. 3 is an enlarged sectional view of a three-way valve actuated by a snap-action mechanism replacing the micro switches forming part of the systemsof FIGS. 1 and 2; a

FIG. 4a is a diagrammatic view of a pneumatic bistable switch according to our invention replacing certain of the microswitches in the system of FIG. 2;

FIG. 4b is a front sectional view of the mechanism for prestressing the spring of the snap-action mechanism 'of FIG. 4a;

FIG. 4c is a side sectional view of FIG. 4b;

FIG. 4d isanother view corresponding to that of FIG. 40 but showing the prestressing mechanism thereof and the snapaction spring in a different phase than in -FIG.

5 is a schematic view of a control system fora duplex pump employing the bistable double switch of FIG 4a;

I FIG. 6 is a schematic view of another embodiment of the pump control system of FIG. 5 with the power switches thereof omitted; and

FIG. 7 is a sectional view of a bistable multiple switch for operating a pair of synchronously running pumps in accordance with our invention.

Referring now to the drawings and first particularly to FIG. 1 thereof, there is diagrammaticallyshown'a simplex pump 1 having .diaphragms ormembranes '2 and 3. Liquid which is to be pumped is aspirated through an inlet tube 4 and a check valve4',.and is forced out of the pump 1 through acheck valve 5' and an outlet tube 5. Mechanically controlled three-way valves 6 and 7 and pneumatically controlled three-way valves 8 and 9 cooperate with the pump 1 as well asan on-keying device 10 and an off-keying device 11,

Working gas is initially conducted through a line 12, a pressure-regulated needle valve 13 and a tube 14 to the pneumatically controlled valve or power switch 8,

and isalso fed through a pressure-reducing device 15 (for example at regulating pressure of 1.4 atmospheres excess pressure), through the line 16, the off-keyer 11 and the line17 to the on-keyer 10. If thekey 10' of the on-keying device 10 is depressed, the on-keyer 10 reverses from the position thereof shown in FIG. 1 so that the control gas flows through the lines 18 and 19 into the right-hand chamber of the on-keyer 10, where it maintains the key 10' of the keying devicell) in the initially depressed key position due to pressure of the gas exerted on the membrane 10a in the right hand chamber 10b of the keying device 10. The lines 20,21 and 22 are simultaneously filled with gas. Since the diaphragms of the pump 1 in the inoperative or rest position thereof are forced into a downwardly depressed position by the illustrated spring 1a thereof, the threeoway valve 6, hereinafter referred to as microswitch 6, assumes a setting-opposite to that illustrated' in FIG. 1 due to the pressure of the right-hand switch rod 1b of the pump 1, so that regulating air or gas can flow from the line 22 into the microswitch 6, the line 23 and the microswitch 9. The regulating air passes through the line 24 to the diaphragm of the microswitch 9 and causes a switch-over of the microswitch 9. This switch setting is maintained even when the microswitch 6 is later switched over and the regulating or control air supplied through the line 23 is interrupted, since the reversed switch setting of the microswitch 9 is maintained through the line 20, the microswitch 9 and the line 24. The diaphragm 8d of the power switch 8 is stressed with the regulating pressure through the line 20, the microswitch 9 and the line 25, so that the power switch 8 consequently reverses and opens a path through the line 26 to the diaphragm chamber 3a of the pump 1 for the working gas present in the line 14. Due to the pressure of the working gas, the membrane 3is displaced upwardly as viewed in FIG. 1, so that the microswitch 6 is initially removed from the switch rod 1b of the pump 1 and springs back into the position thereof illustrated in FIG. 1. The line 23 is accordingly vented through the opening 27 of the microswitch 6. When the pump diaphragm .3 attains its highest upper position, as viewed in FIG. 1, the lefthand switch rod actuates the microswitch 7 and reverses it. The regulating or control air or gas present in the line 21 then flows through the microswitch 7 and the line 28 into the microswitch 9, causing reversal of the microswitch 9 into the position illustrated in FIG. 1. Accordingly, the microswitch 6, the lines 23 and 24, the microswitch 9 and the line 25 as well, as the diaphragm chambers relating thereto are all vented through the opening 27. The power switch 8 is thereby restored to the position thereof illustrated in FIG. 1, and vents the diaphragm chamber 31 of the pump 1 through the line 26 so that the membranes 2 and 3 and the switch rods 1b and 10 connected thereto are forced downwardly, as viewed in FIG. 1.

When the membranes 2 and 3 and the switch rods 1b and 1c associated therewith are downwardly displaced, the spring force of the'microswitch 7 is released initially by the left-hand switch rod 10 and the switch 7 springs back to the position shown in FIG. 1. The line 28 is accordingly vented through the opening 27a. The microswitch 9 is maintained in the illustrated position of FIG. 1 by the biasing action of the spring 9b thereof. When the lowermost position of the membrane 3 is reached, the right-hand switch rod 1b of the pump 1 becomes effective and initiates the second working stroke.

If the pump 1 is to be shut off, pressure is applied to the key 11' of the off-keying device 11 so that the switch lever 11c thereof snaps out of the position as shown in FIG. 1 so as to block the supply of regulating air from the line 16 to the line 17. The lines 17, 18 19, 22, 20 simultaneously vented, the spring force of the on-keyer 10 becomes effective and the on-keyer 10 snaps back to the position illustrated in FIG. 1. If the off-keyer 1 1 is not actuated any longer, it returns to the position shown in FIG. 1 and permits the regulating air to flow in the line 17. By depressing the key 10' of the on-keyer 10, the pump 1 can again be placed in operation.

In the simplex pump 1 shown in FIG. 1, the pneumatic three-way valves operate with a regulating pressure, conventional in flow system technology, of substantially 1.4 atmospheres excess pressure, and regulate the power switch 8 which is designed for a higher working pressure adjusted to the simplex pump, such as 10 atmospheres excess pressure, forexample. If the pump 1 should be operated, however, only with a working pressure up to 1.5 atmospheres excess pressure, the pressure reducer 15 and the power switch8 are not applicable. The microswitch 9 can then be connected directly to the simplex pump 1.

In accordance with another embodiment of our invention, a duplex pump can be regulated with mechanically actuated or mechanically and pneumatically actuated three-way values. Such an embodiment is shown schematically in FIG. 2.

The supply of the working gas is effected in the embodiment of FIG. 2 through a line 31 and then, on the one hand, through a pressure-regulated needle valve 32 and lines 33 and 34 to a power switch 35 and through a line 36 to a power switch 37, and, on the other hand, through a pressure reducer 38, a line 39, an off-keyer 40 and lines 41 and 42a to an on-keyer 43. From the line 41, a line 42b extends to a microswitch 44, a line 45 extends to a microswitch 46, and lines 45 and 47 extend to a microswitch 48. The duplex pump 49 is shown in FIG. 2 in idle or inoperative position. When the onkeyer 43 is actuated, the switch lever 43c thereof snaps upwardly as viewed in FIG. 2, and the gas present in the line 42a flows through the on-keyer 43 and lines 50 and 52 into the lower diaphragm chamber 35a of the power switch 35. The power switch 35 is thereby reversed and the working gas in the line 34 flows through the power switch 35 and a line 53 into the right-hand diaphragm chamber 49a of the duplex pump 49 causing displacement of the diaphragms 49, 49" and 49" and the switch rods 49b and 490 of the pump 49 toward the lefthand side of FIG. 2. Simultaneously, regulating gas passes from the line 50 through a line 54 into the lower diaphragm chamber 55a of a microswitch 55 and reverses the latter. The regulating gas in line 56 can then flow through the microswitch 55 and the lines 57 and 54 into the lower diaphragm chamber 55a of the microswitch 55. In this manner, the regulating pressure pulse transmitted from the on-keyer 43 is held or maintained even when the on-keyer 43 is no longer actuated and has snapped back to the initial position thereof as illustrated in FIG. 2. From a line 57, regulating gas, moreover, flows through a line 58 into the upper diaphragm chamber 44b of the microswitch 44 and adds to the spring force therein. This condition is maintained until the diaphragms 49', 49" and 49" of the pump 49 have been forced so far toward the left-hand side of FIG. 2 that the upper right-hand switch rod 49b of the pumps 49 compresses the spring 46b in the microswitch 46 and reverses the valve therein. Consequently, the regulating gas flows from the line 45 through the microswitch 46, a line 59, the left-hand chamber 44c of microswitch 44 and lines 60 and 61 into the lower diaphragm chamber 44a of the microswitch 44. Reversal of the microswitch 44 does not occur yet, however, because the force of the spring 44' and the regulating gas pressure from the line 58 counteract oneanother. The regulating gas also flows through a line 62 into the upper diaphragm chamber 55b of the microswitch 55 so that the latter switches back to the position shown in FIG. 2. The lines 58, 57, 54, 52, 51 and 50 are accordingly vented through a line 63 and the microswitch 48. Due to the venting of the line 58, the microswitch 44 then also reverses, and the regulating gas from the line 42b travels through the lines 60 and 61 to retain. the microswitch 44 in the reversed position thereof. Through a line 64 the regulating gas is then conducted to the power switch 37 causing the reversal thereof so that working gas is passed from the line 36 through the power switch 37 and a line 65 into the left-hand diaphragm chamber 49d of the duplex pump 49. The working diaphragm 49", discharging diaphragms 49' and 49" and the switch rods 4% and 490 of the duplex pump 49 are displaced toward the right-hand side of FIG. 2.

Due to the aforementioned venting of the line 52, the power'switch 35 switches over to the position shown in FIG. 2 so that the right-hand diaphragm chamber 49a of the pump 49 is vented through the line 53 and the power switch 35. Due to the displacement of the pump diaphragms toward the right-hand side of FIG. 2, the force of the spring 46b of the microswitch 46 is released causing reversal of the latter tothe position shown in FIG. 2.-The line 59 is thereby vented through the microswitch 46. The displacement of the pump diaphragms toward the right-hand side of FIG. 2 continues until the left-hand switch rod 49c of the pump 49 reverses the microswitch 48 and the regulating gas present in the line 47 flows through the microswitch 48, the line 63, the microswitch 55 and the lines 57, 58, 54, 52, 51v and, 50 and the switching operations are repeated.

Shutdown of the pump 49 is effected by actuating i.e., depressing, the key 40' of the ofl keyer 40. The feeding of regulating gas from the line 39 to the line 41 is thereby interrupted. Venting of the regulating gas lines 41, 42a, 56, 42b, 45 and 47 is produced simultaneously. The power switches andmicroswitches receive no regulating gas and switch back to the positions thereof shown in FIG. 2 due to the automatic action of the related spring forces. Also, the pump 49, no longer subjected to working gas, remains in the mean position shown in FIG. 2. The system of FIG. 2 can again be set in operation by actuating or depressing the key 43 of the on-keyer 43.

Obviously the pumps 1 and 49, shown respectively in FIGS. 1 and 2, can also be operatedwithout on and offkeyers. The start-up and shut-down of the pump can then be effected solely through the needle valves 13 and 32, respectively, of the systems of FIGS. 1 and 2.

The aspiration of the'liquid is produced in the system of FIG. 2 through a tube 66, and further advancement of the liquid is effected through a tube 67, suitable and necessary check valves 66' and 67 being provided in the aspirating or suction tube 66 and in the pressure tube 67.

As mentioned hereinbefore, the valve-regulated differential pump is controllable infinitely or continuously from zero to maximum i.e., not in stages or steps, a needle valve being employed conventionally for quantity regulation.

According to anotherembodiment of our invention, the pump can be infinitely variable controlled from zero to maximum by placing the pump withthe control its maximum discharge or advancing output at the required minimum pressure.

Such quantity regulation is suited primarily for those cases wherein the pump advances a fluid fuel, for example CH OI-I, into .a pressure. vessel (reformer) wherein the fluid substance is subjected to catalytic decomposition and, from the gas that is formed, such as hydrogen and C0 for example, the hydrogen is converted into electrical energy in a fuel cell. The hydrogen thus formed andpurified, if desired, is ini: tially employed as regulating and working gas of the pump, and subsequently consumed in a fuel cell battery connected therewith. The gas pressure in. the aforedescribed vessel and the quantity of liquid pumped thereby vary in dependence on the demand for hydrogen by the fuel cell. Accordingly, when hydrogen consumption increases, the pressure in the vessel is reduced and the output of the pump is thereby increased. When hydrogen consumption drops, then conversely the pressure is increased and the pump output is throttled back. This quantity regulation is hereinafter described in greater detail with respect to FIGS. 5 and 6.

For pumps with especially low output, it is recommended, according' to a further feature of our invention, to substitute three-way valves operated by snapaction mechanisms for the microswitches 6, 7, 46 and 48 shown in FIGS. 1 and 2. Such valves operated by snap action mechanisms afford pneumatic control even for very low piston speed. A snap-action switch of this type is shown diagrammatically and in section in FIG. 3, and includes a pressure pin'71 displaceable by engagement of a pump switch rod therewith so that the pressure pin 71 transmits pressure through a leaf spring7 2a and a IJ-shaped spring 72b to a switch lever 73 which, after pivoting through a specific traversed distance, results in forward snapping of the U-spring 72b and the lever '73. Similarly, upon the release and restoration of the pressure pin 71, a rapid snap-back of the lever 73 occurs, so that pneumatic regulation also for a very low piston speed i.e., for minimal output of the pump, is possible. Valve tubes 74, and 76 necessary for regulating the pump are also provided. Introduction of regulating gas to the snap-action valve of FIG. 3 is effected through the tube 74 and the further transmission of regulating gas into the diaphragm space of a pump is effected through the tube 76. The tube 75 is provided to aflord the required venting of the gas.

Two levers 73 for switching over two three-way valves simultaneously can be linked to the U-shaped spring 72b. If two monostable three-way valves such as that of FIG. 3 are operated by a common U-shaped spring 72b and if the required switch path or traversed distance for actuating the snap-action mechanism is selected so that it equals the piston travel of the pump or is adjusted thereto by a simple lever transmission,

this combination can then replace a bistable double switch with pressure-relieved valves. Pressure relief of the common U-shaped spring 72b, the leaf spring 72a and the pressure pin 71 is effected because the forces on both valve plates are the same but act in opposite directions on levers 73 that are connected to one another, since both valves can be operated with the same regulating pressure and the valve openings can be given the same diameter. Then only one switch rod has to be extended from the differential pump so as to actuate the common pressure pin 71 of the double snap-action valve. 7

According to a further embodiment of our invention, a bistable snap-action mechanism can be employed instead of the monostable snap-action mechanism of FIG. 3, and can be combined with two to four pneumatic three-way valves. Such a bistable multiple switch is suited as a double switch primarily for regulating duplex pumps. By the use thereof, the three-way valves 44 and 55 installed in the system of FIG. 2 as holder relays are superfluous. Furthermore, as in the case of the monostable snapaction mechanism of FIG. 3, switching speed and switching force are independent of release speed and release force i.e., even for low discharge outputs of the pump, operational reliability is provided. A pneumatic bistable switch and a system incorporating the same according to this added feature of our invention are shown in FIGS. 4a to 4d and 5.

As shown diagrammatically in FIG. 4a, a bistable snapaction mechanism 77 is operatively connected to a pair of pneumatic three-way valves 78 and 79. Regulating or control gas enters the valves 78 and 79 respectively through tubes 81 and 80 and passes through tubes 82 and 83 respectively into the left-hand and right-hand diaphragm chambers of a duplex pump (not shown in FIG. 4a). The regulating gas is vented through the tubes 84 and 85. Lever arms 86 and 87 are pivotally mounted at the points 88 and 89, respectively. Both lever arms 86 and 87 are connected through a bow 90a by means of an articulating joint with a prestressed leaf spring 91 forming part of the snap-action mechanism 77 and stressed, for example, with a force of 200 pounds. Prestressing is effected, as shown in FIG. 4b, by bracing the spring 91, with its back on a sliding carriage 95, toward the lower part of the housing 97, as viewed in FIG. 4b, with a force of 200 pounds, a reaction force of 100 pounds being respectively exerted on the levers 86 and 87 through the bow 90a. If a force of more than 200 pounds is exerted on the plunger 96, the latter and the carriage 95 are displaced downwardly, as viewed in FIG. 4b, and the spring 91 is then stressed by more than 200 pounds. (The compression spring 95 located within the carriage 95 is stressed with about 500 pounds and should have a damped operation only if very sharp blows having a force of more than 500 pounds are exerted on the plunger 96.) The leaf spring 91 is bent downwardly and snaps into the position shown by the dotted line in FIG. 4b and by the solid line in the side sectional view of FIG. 4d when about 230 pounds of force is applied thereto through the plunger 96. Thereby, the bow 90a, as illustrated in FIG. 4a, is simultaneously displaced snappingly from the position shown by the dotted lines into the extended position thereof as shown in solid lines, and the levers 86 and 87 accordingly switch over. As shown in the sectional views of FIGS. 4b and 4d, the leaf spring 91 engages the lower slide carriage 92 in its newly attained position. A result thereof is that the slide carriage 92 moves downwardly from the position thereof in FIG. 4c to that shown in FIG. 4d. Accordingly, the spring 93 is stressed against the lower part of the housing 97 with a force of 200 pounds, according to the hereinbefore described example, and that force is transmitted through the leaf spring 91 to the bow 90.

If a force is then applied to the plunger 98 in direction of the upwardly directed arrow shown in FIG. 4d, the sliding carriage 92, reinforced by the force of the spring 93, is displaced upwardly, and the leaf spring 91 is accordingly bent upwardly. The spring 91 snaps back into the position illustrated in FIGS. 4band 4c when a load of about 230 pounds is applied thereto. The bow a and the sliding carriage are simultaneously'snappingly restored to the initial position thereof, and the leaf spring 91 is prestressed with the aforementioned force of 200 pounds. By applying pressure to the plunger 96, the leaf spring 91 is again brought to the snapping position and a new switching operation is introduced. Just as in the sliding carriage 95, a damping spring can also be mounted in the sliding carriage 93. For pumps with very low piston speeds, damping springs can be dispensed with. I

The aforedescribed bistable double switch for controlling a duplex pump is shown installed in the system illustrated in FIG. 5. The pump 116 is to be operated with gas at about 10 atmospheres'excess pressure, for example with the rinsing gas from a palladium-silver diffusion cell. The fact that the gas is at a pressure of about 10 atmospheres excess pressure makes it necessary to install two power switches 101 and 102 in the system of FIG. 5. Quantity regulation takes place therein by disposing the pump 116 and the control members in a vessel represented by the dot-dash lines 103 wherein the pressure varies continuously with the associated consumer. The vessel 103 serves simultaneously as supply vessel for the associated consumer, namely, in the embodiment of FIG. 5, to supply the gas burner of a reformer. The effective surfaces or areas of the pump diaphragms 116', 116," and 116" are given such dimensions that the pump 116 produces maximum output for a pressure of about 0.1 atmospheres excess pressure in the vessel 103 and becomes inoperative when the pressure in the vessel 103 is 1.0 atmosphere excess pressure.

The gas mixture that is produced in a reformer is passed through a palladium-silver diffusion cell to remove the CO therefrom. The gas thereby discharging from the Pd-Ag diffusion cell and which is to be supplied to the burners of the reformer at a pressure of 0.05 atmospheres excess pressure is initially fed through the lines 104 and 105 to the power switch 101 as working gas at that pressure and is conducted through the line 106 to the power switch 102. The rinsing or working gas flows simultaneously from the line 104 through the line 107 to the pressure reducer 108, which reduces the pressure of the rinsing gas to the conventional regulating pressure of 1.4 atmospheres excess pressure, and through the lines 109 and 110 to the three-way valve 111 of the double switch. Further on, the gas flows from the line 112 to the three-way valve 113. In the position illustrated in 9 FIG. 5, the three-way valve 113 for the regulating or control gas is opened so that the gas travels through this valve 113 and the line 114 into the diaphragm chamber 102b of a power switch 102 and reverses the latter. Consequently, the travel-path for the working gas in the line 106 is now free so that the gas can flow through the power switch 102 and the line 115 into the left-hand diaphragm chamber 116a, as viewed in FIG. 5, of the pump 116. Thus, the working diaphragm 116"is subjected to pressure, and the diaphragms116, 116" and 116" and switch rods 1 16b and 1160 are all moved toward the right-hand side of FIG. 5. The right-hand diaphragm chamber 116d of the pump 116 is, at this instant, vented through the line 1 17 and the power switch 101. The displacement of the pump diaphragms toward the right-hand side of FIG. is ended when the lefthand switch rod 116b of the pump engages the plunger 118a of the bistable double switch and snaps the leaf spring 1 18 of the snap-action mechanism and the threeway valve 113 therewith from the illustrated solid line position thereof to the illustrated dotted line position thereof. The feeding of regulating gas from the line 112 to the line 114 through the three-way valve 113 is thereby blocked; and the line 114 and the diaphragm chamber 102b of power switch 102 are vented through the three-way valve 113. Due to the consequently effective force of the spring 102' in the power switch 102, the latter reverses to the position thereof shown in FIG. 5. Discharge of the working gas from the line 106 is thereby blocked and the left-hand diaphragm chamber 116a of the pump 116 is vented through the line 115 and the power switch 102. With the aforementioned reversal of the three-way valve 113 and snapping of the leaf spring 118, the three-way valve 111 simultaneously reverses so that the lever 118b thereof assumes the position shown by the dotted line. The regulating gasin the line 110 is consequently freed for travel so that it passes through the three-way valve 1 1 1 into the line 1 19 and the diaphragm chamber 101b of the power switch 101, the pressure of the gas causing the power switch 101 to reverse. Then the working gas flows from the line 105 through the power switch 101 and the line 117 into the right-hand diaphragm chamber 116d of the pump 116, subjects the working diaphragm 116" to pressure and thereby displaces the diaphragms and switch rods of the pump 116 toward the left-hand side of FIG. 5. This displacement is maintained until the right-hand switch rod 1160 of the pump 1 16 contact the bistable switch plunger 118a and reverses the switch through snapping of the leaf spring 118 back to the extended position thereof represented by the solid line in FIG. 5. Thereafter, a new operating cycle of the system shown in FIG. 5 can be started.

The influx of fuel to be advanced in the non-illustrated reformer, for example a mixture of methanol and water having a molar ratio of 1:l,,occurs in the'system of FIG. 5 through the tube 120, and the outflow thereof is through the tube 121. The withdrawal of gas for the gas burners employed to heat the reformer is effected from the vessel 103 through a line 123 provided with a suitable pressure-reducing device 122. r

The power switches 101 and 102 of the system shown in FIG. 5 can be dispensed with if the introduced working gas has a pressure that does not exceed 1.5 atmospheres excess pressure. The duplex pump 116, in

such a case, stops operating when the pressure in the vessel 103 is 1.0 atmosphere excess pressure having however attained its maximum output at a backpressure of about 0.6 atmospheres excess pressure, because a prepressure of 0.5 atmospheres excess pressure required for the fuel cell must be assured.

Such a system, with power switches dispensed with, is shown in FIG. 6. The working gas, for'example hydrogen derived from a reformation process and purifled throughan alkaline bath, issupplied through a line 131 to a duplex pump 132 and through a line 133 and a line 135, respectively, to three-way valves 134 and 136. In the solid line positions of the leaf spring 139 and the respective levers 13% and 1390, thethreeway valve 136 is open and the hydrogen. working gas flows through the line 137 into the right-hand diaphragm chamber 132d of the pump 132. The working diaphragm 132'. is subjected to the pressure of the hydrogen working gas and consequently is displaced with the other diaphragms 132' and 132" and switch rods 132b and 132ctoward the left-hand side of FIG. 6.

The left-hand diaphragm chamber 132a of the pump 132 is accordingly vented through a line 138 and the three-way valve 134. The displacement ends when the right-hand switch rod 1320 contacts the plunger 139a of the snap-action spring mechanism 139 of the illustrated bistable double switch, and reverses the latter to the dotted-line position of the spring .139 and levers 13% and 1390 thereof. The right-hand diaphragm chamber 132d of the pump 132 is thereby vented through the line 137 and the three-way valve 136, the left-hand diaphragm chamber 132a of the pump is filled, through the three-way valve 134 and the line 138, with hydrogen gas present in the line 133, and the pump diaphragms 132, 132" and 132" as well as the switch rods 1152b and 132a are again displaced toward the righthand side of FIG. 6. Thedisplacement thereof ends when the left-hand switch rod 132b of the pump 132 contacts the plunger 139a of the'bistable switch snap-switch mechanism 139'and reverses the switch to the illustrated position of the levers 13% and 13% shown in solid lines.

The hydrogen working gas leaves the containing vessel M2 through a valve 145 and a pressure reducer 140 in a line 141 through which it flows into a fuel cell battery which, for the sake of clarity, is omitted from FIG. 6. The influx of vapor or gas containing hydrogen into the pump 132 is efiected through the line 143, and into the non-illustrated reformer through the line 144 from the pump 132.

The embodiment of the system of our invention shown in FIG. 6 can be further improved by seating or installing the three-way valves 134 and 136 on the housing of the pump 132. The lines 137 and 138 can thereby be dispensed with, and the detrimental spaces (dead volume or spaces) reduced.

According to a further embodiment of our invention, the bistable snap-action mechanism can be equipped with pressure-relieving valves. This has the primary advantage that the valve covers are closed with the same force both on the pressure side as well as on'the exhaust side thereof. By pressure-relieving the three-way valves, a working gas at higher pressure, up to about 10 atmospheres excess pressure, can be introduced as regulating gas, i.e., power valves or switches are not required up to a pressure of atmospheres excess pressure.

In FIG. 7 there is shown a bistable quadruple switch for operating a pair of synchronously running pumps, wherein the bistable snap-action mechanism 150 is combined with four pressure-relieved three-way valves 151, 152, 153 and 154. By applying pressure to a plunger 155, in a manner corresponding to that aforedescribed with respect to the embodiment of FIG. 6, a leaf spring 156 and a bow 157 are caused to'snap into a reverse position. Consequently, valve holders 158, 159, 160 and 161 are drawn downwardly to the illustrated position thereof and of the respective valve members 152 and 154 in FIG. 7. Vent openings 162 and 163 are thus closed by the valve members or heads 151 and 154, and working gas or vapor flows through openings 164, 165, 166 and 167.into'the diaphragm chambers .of non-illustrated pumps connected to the switch. The vent openings 168 and 169 are thereby opened so that the working gas can flow through the openings 170 and 171 out of the working chambers of the nonill'ustrated pumps connected to the switch of FIG. 7. The ball valves 152 and 153 thereby close the valve chambers and thus prevent the flow of working gas to the valve chambers through the openings 172 and 173.

When the diaphragms and switch rods of the nonillustrated pumps reach their end position, in a manner similar to that for the embodiment of FIG. 6, pressure is exerted on the plunger 178, the leaf spring 156 and the bow 157 reverse, and the valve holders 158 161 are displaced in the opposite direction. The vent openings 162 and 163 are thereby opened, and the working gas flows through the openings 165 and 166 out of the diaphragm chambers of the non-illustrated pumps, so that venting occurs. Simultaneously, the openings 172 and 173, through the inlets 170 and 171, are freed for admitting working gas into the diaphragm chambers of the non-illustrated pumps, and the piston rods or switch rods of the pumps are displaced in the opposite direction. The vent openings 168 and 169 are thus closed, so that discharge of the working gas therethrough is prevented.

Pressure relief of the valve seat is effected in the embodiment shown in FIG. 7 in the following manner: The working gas is under predetermined pressure in the inlet lines 164 and 166 and exerts a force on the valve members corresponding to the diameter of the respective valve opening. Since the seals 179, 180, 181 and 182 on the other side of the valve members have the same diameter as the valve openings, a force of the same value, though displaced 180 from one another, is exerted respectively on the valve members and the seals.

The valve holders accordingto our invention are formed, preferably, of a metal rod and are connected to a collar. The ball-shaped valve members consist, for example, of known plastic materials such as multi-component gluten or epoxide resin and are formed with the aid of ball-shaped collets made of glass or ,teflon, and are mounted on the valve holders. Advantageously, the ball-shaped valve members formed of plastic material are elongated in the form of a tube so that they surround the metal rod valve holders and are pressed against the elongated holders by the pressure of the gas present in the respective valves.

The pumps according to our invention are primarily suited for advancing and metering small quantities of liquid, for example fluid fuel or oxidizer in fuel cells or in a reformer of a fuel cell installation. Circulation of electrolytic or coolant in fuel cells can also be effected by means of the improved differential pumps of our invention. Rinsing gas leaving a Pd-Ag diffusion cell as well as gas discharging from a reformer can be introduced as regulating or working gas to the differential pump of our invention. Furthermore, gas such as hydrogen or oxygen stored in pressure bottles or tanks can be employed for operating the differential pumps of our invention.

We claim:

1. Valve-controlled differential pump system for advancing and metering liquids, comprising a differential pump having a driving chamber and piston rod means actuable in response to fluid pressure exerted in said driving chamber, and means for controlling said pump including at least one mechanically actuable three-way valve operatively connected to the driving chamber of said pump, at least one snap-action mechanism comprising a spring leaf, a plunger operatively engageable with said spring leaf for mechanically actuating said snap-action mechanism, lever means connected to said differential pump piston rod means and operable thereby for actuating said plunger, and at least two three-way valves pneumatically actuable by the fluid of said differential pump, said pneumatically actuable three way valves being connected in connecting lines between said mechanically actuable three-way valve and said driving chamber.

2. Valve-controlled differential pump system for advancing and metering liquids, comprising a differential pump having a driving chambe'r'and piston rod means actuable in response to fluid pressure exerted in said driving chamber, and means for controlling said pump including at least one mechanically actuable three-way valve operatively connected to the driving chamber of said pump, at least one snap-action mechanism comprising a spring leaf, a plunger operatively engageable with said spring leaf for mechanically actuating said snap-action mechanism, and lever means connected to said differential pump piston rod means and operable thereby for actuating said plunger, said three-way valve being connected with said snap-action mechanism and having a pair of openings, said snap-action mechanism being monostable and comprising a leaf spring and a switch lever connected to one another by a U-shaped spring, said snap-action mechanism being actuable by said plunger for snapping said switch lever into alternate position in which it closes one of said pair of openings respectively.

3. Valve-controlled differential pump system for advancing and metering liquids, comprising a differential pump having a driving chamber and piston rod means actuable in response to fluid pressure exerted in said driving chamber, and means for controlling said pump including at least one mechanically actuable three-way valve operatively connected to the driving chamber of said pump, at least one snapaction mechanism comprising a spring leaf, a plunger operatively engageable with said spring leaf for mechanically actuating said snap-action mechanism, lever means connected to said differential pump piston rod means and operable thereby for actuating said plunger, at least two threeway valves having respective pairs of openings, and including a snap-action mechanism associated with said two three-way valves, said snap-action mechanism being monostable and comprising a leaf spring and a pair of switch levers connected to said leaf spring by a U-shaped spring, said snap-action mechanism being actuable by said plunger for snapping said switch levers into alternate positions for simultaneously closing one of the openings in each of said pairs of openings.

4. Valve-controlled difierential pump system for advancing and metering liquids, comprising a differential pump having a driving chamber and piston rod means actuable in response to fluid pressure exerted in said driving chamber, and means for controlling said pump including at least one mechanically actuable three-way valve operatively connected to the driving chamber of said pump, at least one snap-action mechanism comprising a spring leaf, a plunger operatively engageable with said spring leaf for mechanically actuating said snap-action mechanism, lever means connected to said differential pump piston rod means and operable thereby for actuating said plunger, and at least two snap-action mechanisms, respectively connected to said three-way valves, each of said snap-action mechanisms being bistable and comprising a prestressed leaf spring, articulatingly connected to a bow member and disposed on a sliding carriage, said bow member being connected to a pair of levers displaceable in response to snapping of said leaf spring for simultaneously reversing said three-way valves.

5. Differential pump system according to claim 4 including at least two valve holders force-lockingly connected in tension and compression to said bow, for simultaneously reversing at least two pressure-relieved three-way valves. 

1. Valve-controlled differential pump system for advancing and metering liquids, comprising a differential pump having a driving chamber and piston rod means actuable in response to fluid pressure exerted in said driving chamber, and means for controlling said pump including at least one mechanically actuable three-way valve operatively connected to the driving chamber of said pump, at least one snap-action mechanism comprising a spring leaf, a plunger operatively engageable with said spring leaf for mechanically actuating said snap-action mechanism, lever means connected to said differential pump piston rod means and operable thereby for actuating said plunger, and at least two three-way valves pneumatically actuable by the fluid of said differential pump, said pneumatically actuable three-way valves being connected in connecting lines between said mechanically actuable three-way valve and said driving chamber.
 2. Valve-controlled differential pump system for advancing and metering liquids, comprising a differential pump having a driving chamber and piston rod means actuable in response to fluid pressure exerted in said driving chamber, and means for controlling said pump including at least one mechanically actuable three-way valve operatively connected to the driving chamber of said pump, at least one snap-action mechanism comprising a spring leaf, a plunger operatively engageable with said spring leaf for mechanically actuating said snap-action mechanism, and lever means connected to said differential pump piston rod means and operable thereby for actuating said plunger, said three-way valve being connected with said snap-action mechanism and having a pair of openings, said snap-action mechanism being monostable and comprising a leaf spring and a switch lever connected to one another by a U-shaped spring, said snap-action mechanism being actuable by said plunger for snapping said switch lever into alternate position in which it closes one of said pair of openings respectively.
 3. Valve-controlled differential pump system for advancing and metering liquids, comprising a differential pump having a driving chamber and piston rod means actuable in response to fluid pressure exerted in said driving chamber, and means for controlling said pump including at least one mechanically actuable three-way valve operatively connected to the driving chamber of said pump, at least one snap-action mechanism comprising a spring leaf, a plunger operatively engageable with said spring leaf for mechanically actuating said snap-action mechanism, lever means connected to said differential pump piston rod means and operable thereby for actuating said plunger, at least two three-way valves having respective pairs of openings, and including a snap-action mechanism associated with said two three-way valves, said snap-action mechanism being monostable and comprising a leaf spring and a pair of switch levers connected to said leaf spring by a U-shaped spring, said snap-action mechanism being actuable by said plunger for snapping said switch levers into alternate positions for simultaneously closing one of the openings in each of said pairs of openings.
 4. Valve-controlled differential pump system for advancing and metering liquids, comprising a differential pump having a driving chamber and piston rod means actuable in response to fluid pressure exerted in said driving chamber, and means for controlling said pump including at least one mechanically actuable three-way valve operatively connected to the driving chamber of said pump, at least one snap-action mechanism comprising a spring leaf, a plunger operatively engageable with said spring leaf for mechanically actuating said snap-action mechanism, lever means connected to said differential pump piston rod means and operable thereby for actuating said plunger, and at least two snap-action mechanisms, respectively connected to said three-way valves, each of said snap-action mechanisms being bistable and comprising a prestressed leaf spring, articulatingly connected to a bow member and disposed on a sliding carriage, said bow member being connected to a pair of levers displaceable in response to snapping of said leaf spring for simultaneously reversing said three-way valves.
 5. Differential pump system according to claim 4 including at least two valve holders force-lockingly connected in tension and compression to said bow, for simultaneously reversing at least two pressure-relieved three-way valves. 